Ignition primer for photoflash lamps



Nov. 18; 1941. D. LOCKWOOD 2,263,179

IGNITION PRIMER FOR PHOTOFLASH LAMPS Filed D80. 30, 1938 INVENTOR L .D. ZOC'KWflOD WWW?- ATTORNEY Patented Nov. is, 1941 2,263,179 v IGNITION PRIMER FOR PHOTOFLASH LAMPS Lloyd D. Lockwood, Madison,

N. 3., assignor to Westinghouse Electric & Manufacturing Company, East Pittsbur Pennsylvania Pa., a corporation of Application December 30, 1938, Serial No. 248,402

3 Claims,

The present invention relates to what are known to the art as photo flash lamps and more particularly to the primer which ignites the combustible material for generating actinic light.

Lamps of this type are well known in the art and as heretofore constructed, the primer consists of fine metal powders such as zirconium, magnesium, aluminum, etc., and an oxidizing material, such as lead peroxide. These primer materials are usually ignited by the passage of an electric current through a filament, such as tungsten or the like, embedded in or coated with the primer material. In many instances, however, the filament burns out upon the application of current thereto without the primer being actually ignited which results in the lamp failing to flash.

It is accordingly an objector the present invention to provide a photoflash lamp wherein ignition of the primer is facilitated so that nonflashing of the lamp is substantially eliminated.

Another object of the present invention is the provision of a photoflash lamp wherein the filament which functions as the igniter for the primer is coated with a film of inflammable material to ensure ignition of the primer followed by flashing of the lamp.

A further object of the present invention is the provision of a primer for a photofiash lamp wherein the filament which ignites the primer is coated with a continuous film of inflammable material of such nature that whenever the fila-' ment has been raised to a temperature sufiiciently high to fuse the filament, the inflammable material will be volatilized and ignited in the oxidizing atmosphere within thelamp.

Still further objects of the present invention will become obvious to those skilled in the art by reference to the accompanying drawing wherein:

Fig. 1 is an elevational view of a photoflash lamp constructed in accordance with the present invention, and

Fig. 2 is a sectional view showing the construction of the primer as used in the lamp shown in Fig. 1.

Referring now to the drawing in detail, the lamp shown in Fig. 1 comprises an evacuated vitreous envelope or bulb 5 which, after evacuation, is provided with oxygen or a, gaseous oxygenic substance, such as lead peroxide or the like, which produces oxygen. The envelope as shown is provided with a reentrant press 6 and a standard type threaded screw base i.

A pair of leading-in conductors 8 and 9 extend from the base I through the press portion of the envelope to the interior thereof, and at their extremity are interconnected by a filament H] which may be of tungsten, nickel, or other suitable metal, which readily fuses upon the passage of an electric current therethrough. In accordance with the present invention, this filament I0 is first coated with a continuous film of inflammable material [2 of such nature that when the filament is raised to a temperature sufiiciently high to fuse the filament, the inflammable.material will be volatilized and ignited in the oxidizing atmosphere of the lamp.

Any material having these characteristics may be employed, such for example as very fine red phosphorus and a nitrocellulose binder dissolved in amylacetate and a plasticizer di-brityl pthalate, or a mixture of potassium chlorate or potassium chromate together with antimony trisulphide. This inflammable material may be applied by dipping the filament l0 together with the tips of-the leading-in conductors 8 and 9 into the material and allowing to dry.

After precoating the filament with the inflammable material l2, the primer B, which may consist of the fine metal powders of zirconium, magnesium, aluminum and an oxidizing agent such as lead peroxide, is then applied, as is well known in the art. Inasmuch as the primer, after application, is in the form of powder and thus subject to flaking due to jarring as well as possible inadvertent ignition due to heat during the sealing-in operation, it may be desirable to further coat the primer. Accordingly, the primer may be coated with a suitable material H, such for example as cellulose acetate, by dipping the primer in the material and allowing to dry, which material may extend an appreciable distance down the leading-in wires, as shown in Fig. 2.

Upon completion of the primer as above noted, the envelope is filled with a. readily combustible material, such as aluminum foil or magnesium wire i5, and the stem, supporting the completed primer, sealed to the envelope in the customary manner. It will thus become obvious to those skilled in the art that a photoflash lamp is herein shown and described wherein the filament is provided with an undercoating of a continuous film of inflammable material which ensures ignition of the primer prior to fusion of the filament, thus substantially eliminating non-flashing of the lamp by failure of the filament to'ignlte the primer prior to fusion.

Moreover, this undercoating of phosphorus and nitrocellulose or the like prevents the heavy metal powders in the primer from cooling the filament and so allows the latter to evenly heat up over a considerable length, igniting first thecoating which in turn ignites the primer, thus further ensuring ignition of the primer before fusion of even a low melting point filament.

Although one embodiment of the present invention has herein been shown and described, it is to be understood that other modifications oi the same may be made without departing from the spirit and scope of the appended claims.

I claim: i

1. An igniting device for facilitating combustion of combustible material in a photoflash lamp comprising a filament adapted to fuse upon the passage of the current therethrough, a continuous coating of highly inflammable material applied to said filament, a primer material rapidly combustible with oxygen superimposed on said inflammable material, and a coating on the outer surface of said primer to prevent external heat from inadvertently igniting said primer or causing flaking thereof.

2. An igniting device for facilitating combustion of combustible material in a photoflash lamp comprising a filament adapted to fuse upon the passage of the current therethrough, a highly inflammable primer material rapidly combustible iii with oxygen surrounding said filament, and a coating formed of red phosphorus and nitrocellulose binder dissolved in amyl acetate and a plasticizer di-butyl phthalate, superimposed between said primer material and said filament to prevent said primer material from cooling said filament and to enable the latter to become evenly heated over substantially its entire length and ignite said coating with attendant ignition of said primer and combustion of the combustible material in said photoflash lamp.

3. An igniting device for facilitating combustion of combustible material in a photofiash lamp comprising a filament adapted to fuse upon the passage of the current therethrough, a highly inflammable primer material rapidly combustible with oxygen surrounding said filament, and a coating formed of potassium chlorate or chromate and antimony trisulphide interposed between said primer material and said filament to prevent said primer material from cooling said filament and to enable the latter to become evenly heated over substantially its entire length and ignite said coating with attendant ignition of said primer and combustion of the combustible material in said photoflash lamp.'

LLOYD D. LOCKWOOD. 

